Worldwide, diarrhea remains a leading cause of childhood morbidity and mortality, with 2.5 million deaths estimated to occur annually among children < 5 years of age. In the United States, acute gastroenteritis accounts for > 1.5 million outpatient visits, 200,000 hospitalizations and approximately 300 deaths/year. The incidence of diarrhea varies between one and 2.5 episodes per child per year. In Ontario, children account for over 28,000 Emergency Department visits for gastroenteritis annually, and the pediatric admission rate for gastroenteritis remains greater than 400/100,000. In a Toronto based report from 1978, viral gastroenteritis was found as the etiologic agent in the deaths of 21 children over a 5 year period. Over 10% of patients seen at The Hospital for Sick Children ED present with acute gastroenteritis (vomiting, diarrhea or both). Last year over 4500 children with these complaints were seen.